The invention relates to a device for the non-contact control of a sanitary fitting, which can be accommodated, for example, in the wall behind a urinal or a shower, or directly in the sanitary fitting to be controlled.
A device for the non-contact control of a sanitary fitting is disclosed in DE-A-3408261. It comprises:
a) an emitting/receiving unit which includes an emitter which emits radiation into a monitoring space, and a first receiver which receives radiation reflected by an object in the monitoring space; and PA0 b) a circuit arrangement which includes a driving circuit providing a voltage for operating the emitter, the magnitude of which voltage determines the intensity of the radiation emitted, and a first detection circuit to which the output signal of the first receiver is applied and which generates an output signal when the output signal of the first receiver exceeds a certain threshold value. PA0 a) an emitting/receiving unit comprising: PA0 b) a circuit arrangement comprising: PA0 (i) in an initialisation mode, in which the control unit continuously increases the output voltage of the driving circuit, starting at a low value, and puts a value that is representative of that output voltage into the first store when the first detection circuit releases an output signal, and puts a value that is representative of that output voltage into the second store when the second detection circuit releases an output signal, such that there is stored in the third store a value that is representative of the quotient of the output voltages of the driving circuit at which the first detection circuit and the second detection circuit generate a respective output signal, and PA0 (ii) in an adjusting mode, in which the control unit continuously increases the output voltage of the driving circuit, starting at a low value, and puts a value that is representative of that output voltage into the second store when the second detection circuit generates an output signal, such that there is produced in the multiplier a value that is representative of a desired output voltage of the driving circuit, according to which the control circuit brings the output voltage of the driving circuit up to the desired output voltage. PA0 a) an emitting/receiving unit comprising: PA0 b) a circuit arrangement comprising: PA0 (i) in an initialisation mode, in which the control unit continuously increases the amplification of the detection circuits, starting at a low value, and puts a voltage value that is representative of that amplification into the first store when the first detection circuit releases an output signal, and puts a voltage value that is representative of that amplification into the second store when the second detection circuit releases an output signal, such that there is stored in the third store a value that is representative of the quotient of the amplifications of the detection circuits at which the first detection circuit and the second detection circuit generate a respective output signal, and PA0 (ii) in an adjusting mode, in which the control unit continuously increases the amplification of the second detection circuit, starting at a low value, and puts into the second store a value that is representative of the amplification at which the second detection circuit generates an output signal, such that there is generated in the multiplier a value that is representative of a desired amplification of the first detection circuit, according to which the control circuit brings the amplification of the first detection circuit up to the desired amplification.
A problem exists with devices of this kind that the electronic and/or mechanical components age, which can affect the sensitivity of the arrangement as a whole. If the sensitivity decreases during the operating period, for example over a period of years, the monitoring space in which the device responds to any objects present becomes steadily smaller.
This problem is addressed in the device disclosed in DE-A-3408261 as follows: the emitter is continuously operated at such a high output that reflections from stationary objects are received. A long-time mean value is determined from the received signals constantly registered in that manner. The instantaneous value of the received signal is compared with the long-time mean value. Only when there is a certain minimum deviation from that long-time mean value is the circuit arrangement triggered. With these measures, it is possible to achieve both an initial "self-adjustment" of the circuit arrangement to specific surroundings, and also a re-adjustment to compensate for continuous changes in the surroundings and internal ageing processes.
The arrangement of the device disclosed in DE-A-3408261 is that, in order to determine the long-time mean value, the circuit arrangement has to be powered continuously, and to a level at which reflections from stationary objects are detected by the receiver. In cases where the circuit arrangement is to be powered by a battery at all events, this involves unacceptable energy consumption. Furthermore, this known device fails to work when there are no stationary objects in the vicinity from which radiation could be reflected in order to form the long-time mean value.
A device for the non-contact control of a sanitary fitting is disclosed in DE-A-4019927, which has a special operating mode executed at set time intervals, for setting and re-adjusting the sensitivity. In this special operating mode, the output of the emitter is increased in steps until the radiation reflected to the receiver from stationary objects reaches a value at which the detection circuit is triggered. The emitter output is then reduced again slightly and thus reaches a value at which the stationary objects do not quite cause triggering. This device also achieves a self-adjustment both to internal ageing processes and to changes in the surroundings. There is no increased energy consumption with this device. Nevertheless, in this case also, suitable stationary objects that can be used for self-adjustment need to be present.